| Title: |
The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates |
| Authors: |
Broderick, J. W., Drouart, G., Seymour, N., Galvin, T. J., Wright, N., Rosell, A. Carnero, Chhetri, R., Dannerbauer, H., Driver, S. P., Morgan, J. S., Moss, V. A., Prabu, S., Afonso, J. M., De Breuck, C., Emonts, B. H. C., Franzen, T. M. O., Gutiérrez, C. M., Hancock, P. J., Heald, G. H., Hurley-Walker, N., Ivison, R. J., Lehnert, M. D., Noirot, G., Read, M., Shabala, S. S., Stern, D., Sutherland, W. J., Sutorius, E., Turner, R. J., Vernet, J. |
| Publication Year: |
2022 |
| Collection: |
Astrophysics |
| Subject Terms: |
Astrophysics - Astrophysics of Galaxies |
| More Details: |
While unobscured and radio-quiet active galactic nuclei are regularly being found at redshifts $z > 6$, their obscured and radio-loud counterparts remain elusive. We build upon our successful pilot study, presenting a new sample of low-frequency-selected candidate high-redshift radio galaxies (HzRGs) over a sky area twenty times larger. We have refined our selection technique, in which we select sources with curved radio spectra between 72-231 MHz from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. In combination with the requirements that our GLEAM-selected HzRG candidates have compact radio morphologies and be undetected in near-infrared $K_{\rm s}$-band imaging from the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, we find 51 new candidate HzRGs over a sky area of approximately 1200 deg$^2$. Our sample also includes two sources from the pilot study: the second-most distant radio galaxy currently known, at $z=5.55$, with another source potentially at $z \sim 8$. We present our refined selection technique and analyse the properties of the sample. We model the broadband radio spectra between 74 MHz and 9 GHz by supplementing the GLEAM data with both publicly available data and new observations from the Australia Telescope Compact Array at 5.5 and 9 GHz. In addition, deep $K_{\rm s}$-band imaging from the High-Acuity Widefield $K$-band Imager (HAWK-I) on the Very Large Telescope and from the Southern Herschel Astrophysical Terahertz Large Area Survey Regions $K_{\rm s}$-band Survey (SHARKS) is presented for five sources. We discuss the prospects of finding very distant radio galaxies in our sample, potentially within the epoch of reionisation at $z \gtrsim 6.5$.
Comment: 49 pages, 3 figures (one of which is a multi-page figure with 102 separate panels), 9 tables, accepted for publication in PASA |
| Document Type: |
Working Paper |
| DOI: |
10.1017/pasa.2022.42 |
| Access URL: |
http://arxiv.org/abs/2204.08490 |
| Accession Number: |
edsarx.2204.08490 |
| Database: |
arXiv |
